The instant invention relates generally to water mattresses and more specifically to water mattresses having gas filled chambers secured within the water mattress.
Within the last decade, water mattresses have progressed from a diversion to a desirable alternative to a conventional inner spring or foam mattress. Whereas early designs were prone to premature and catastrophic failure caused by rupture of the plastic mattress wall and loss of the water contained therein, improved materials, sophisticated designs and better manufacturing techniques have increased the service life of such mattresses to the point where failure of the plastic mattress wall is uncommon indeed.
Certain characteristics of water mattresses have, however, inhibited even wider acceptance. The foremost problem is weight. A 72 inch by 84 inch by 9 inch king size mattress contains in excess of 31 cubic feet of water which weighs nearly 2,000 pounds. It is apparent why cautious home owners have been discouraged from purchasing such mattresses. It is equally apparent why landlords have prohibited the use of such mattresses in their leaseholds. Attempts to minimize the weight of water mattresses have met with little success. Clearly, the area of a given mattress is a constraint and thus only the thickness can be diminished. However, it has been determined that a mattress thickness of less than approximately 9 inches may render it uncomfortable under certain circumstances.
Other undesirable and related characteristics of water mattresses are the natural harmonic or wave motion and the response to impulse excitation they exhibit. Subjected to a wave generating movement, a water mattress will exhibit decaying simple harmonic wave motion which many users find objectionable. Since water is incompressible, a single pressure-producing impulse will be transmitted undiminished away from the point of application, be reflected off the boundaries of the mattress and also slowly decay. Various approaches have been used to damp the wave motion but they have been relatively unsuccessful. Internal baffles have been placed within a mattress but they frequently generate sloshing noises. Furthermore, since they merely transmit an impulse from one face to the other, they have no absorbing or decaying effect on such a disturbance. The cost of manufacturing an internally baffled mattress also militates against such a design. The use of viscous fluids such as gelatins or mud has also been suggested but their use substantially negatives the generally simple drainage procedure and portability benefits associated with such mattresses.